1. Field of the Invention
This invention pertains to a skin-conditioning composition which is designed to be applied and rinsed off. More specifically, the inventive composition is intended for use in an environment in which it is applied to human skin, and subsequently rinsed away, leaving a skin-conditioning deposit on the skin's surface which is aesthetically acceptable. The composition is surfactant free.
2. Background of the Invention
Various skin-conditioning compositions exist which are intended to be introduced to bath water, and act as a softener or otherwise condition the skin while bathing. Typical skin conditioning agents include mineral oil or synthetic oils, and in bathing compositions, are of relatively low viscosity, for dispersion in the water. Additionally, polymers are known agents for combining with mineral oils in skin softening compositions, per se.
Other cosmetic compositions particularly designed for skin conditioning include those discussed in U.S. Pat. No. 5,152,991, which is directed to cosmetic compositions containing selectively hydrogenated styrene/butylene copolymers. These copolymers are specifically designed to prevent removal of the composition in which they are formulated, from the skin, or at least to prevent easy washing off of the cosmetic formula.
U.S. Pat. No. 5,143,723 is directed to colored lipstick compositions, or "make-up", such as lipstick, nail coloring and the like. The compositions addressed are intended to exhibit particular brilliance of color, by incorporating a solvated dye into the resins, including styrene block polymers or butylene/ethylene copolymers.
An additional cosmetic composition which employs particulate polymers, rather than a polymer matrix, is addressed in European Patent Application 497,144, that requires particulate styrene/ethylene/propylene copolymer components, as well as conventional emollients and agents such as colorants, UV blockers and the like.
A different type of cosmetic composition is addressed in U.S. Pat. No. 5,221,534, DesLauriers et al., the entirety of which is incorporated herein by reference. This reference is directed to compositions employing mineral oil with blends of di-block and tri-block copolymers based on synthetic thermoplastic resins. In general, the compositions contain 80-99% by weight of an oil, and 1-20% by weight of copolymer which includes at least one of either a di-block or tri-block polymer which consist of a hard segment, such as a styrenic segment, and a soft segment, such as butadiene. Thus, tri-block copolymers of styrene/butadiene/styrene and styrene/isoprene/styrene are employed, as well as di-block copolymers such as a styrene/ethylene/propylene, or styrene/ethylene butylene are employed to gel the oil, imparting a substantially different viscosity. The gel is designed as a carrier for various agents for topical administration. This gelled mineral oil is commercially available under the mark Geahlene, from Penreco, Division of Pennzoil products. Certain of the preparations described herein were made with Geahlene AJ.
An alternate formulation is disclosed in U.S. Pat. No. 5,578,299, Starch, and related U.S. patent application Ser. No. 08/861,108. These applications describe compositions that achieve controlled deposition of skin-conditioning agents, or emollients, by careful control over the amount and type of surfactant employed. As recognized in these patent documents, the deposition of too little of the emollient on the skin, after rinsing, as a residue does not provide a significant conditioning effect. In the alternative, too high a percentage of deposition makes rinsing difficult, and leaves the skin with an oily, greasy feeling. As disclosed in U.S. Pat. No. 5,578,299, incorporated herein by reference, a desirable percentage of the formulation left as a residue on the skin after rinsing is about 3-25%, of the formulation, by weight. Preferred amounts include 6-15%, by weight. U.S. Pat. No. 5,578,299 and pending U.S. patent application Ser. No. 08/861,108, achieve control over the amount of emollient deposited in particular, Geahlene, by controlling the amount of surfactant incorporated, and the type of surfactant. The need to use and control surfactant composition carefully, however, limits the range of optional ingredients that can be incorporated in the formulation, and raises the possibility of skin irritation.
While U.S. Pat. No. 5,221,534 provides a method for depositing topical agents without the use of a surfactant, and may itself provide certain skin conditioning properties, since the product is in the form of a gel, deposition directly on the skin leaves an undesirable feeling.
U.S. Pat. No. 5,004,598, Lochhead et al., discloses a quick-breaking water-in-oil emulsion containing mineral oil and a Pemulen polymer that breaks on contact with the skin. The active agent is a modified polymer which is a copolymer having a major proportion of a monoolefinically unsaturated carboxylic acid monomer or its anhydride of 3 to 6 carbon atoms and a minor proportion of a long chain acrylate or methacrylate ester monomer. The disclosure of U.S. Pat. No. 5,004,598 is incorporated herein by reference.
U.S. Pat. Nos. 5,043,155, Puchalaski et al., and 4,837,019, Georgalas et al., describe emollients which contribute to emulsion stability, and are generally comprised of glyceryl polymethacrylate, propylene glycol and a poly(vinyl-methyl ether) maleic anhydride (PVM/MA) copolymer. These compositions are available as Lubragel oil, manufactured by Guardian Chemical, while the emulsion stabilizer comprised of the glyceryl polymethacrylate and propylene glycol, without the PVM/MA is available under the name Lubragel CG. The disclosure of U.S. Pat. No. 5,043,155 is incorporated herein by reference.
Other emollients used in the art for skin conditioning include octyl isononanoate, which is typically used in conjunction with mineral oil, to provide a certain amount of "slip", or reduce the greasy feel provided by mineral oil. U.S. Pat. Nos. 5,527,488 and 4,722,835 exemplify this use.
Carbopol polymers available from B. F. Goodrich have also been explored as possible emulsifiers. These agents are acrylic acid or homopolymers, generally of the formula (C.sub.3 H.sub.4 O.sub.2).sub.n, which are subsequently cross-linked, to give a molecular weight of about 1 million-4 million. U.S. Pat. No. 5,004,598 examines the use of such polymers as emulsifiers in emulsions, column 9, line 50 - column 10, line 2, and finds they lead to unstable emulsions.
None of the compositions available to those of ordinary skill in the art simultaneously provide adequate skin conditioning effect, with a controlled deposition of 3-25% by weight of the composition after rinsing, an acceptable feel, and in the absence of surfactants. The provision of such a skin conditioning formulation continues to be an object of those of skill in the art.